ssl_helpers.c: add mbedtls_test_ssl prefix for *_exchange_data

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
diff --git a/tests/suites/test_suite_ssl.function b/tests/suites/test_suite_ssl.function
index 7960d12..c9178e3 100644
--- a/tests/suites/test_suite_ssl.function
+++ b/tests/suites/test_suite_ssl.function
@@ -3085,10 +3085,11 @@
     server.ssl.session_negotiate->id_len = 33;
     if (options.cli_msg_len != 0 || options.srv_msg_len != 0) {
         /* Start data exchanging test */
-        TEST_ASSERT(mbedtls_exchange_data(&(client.ssl), options.cli_msg_len,
-                                          options.expected_cli_fragments,
-                                          &(server.ssl), options.srv_msg_len,
-                                          options.expected_srv_fragments)
+        TEST_ASSERT(mbedtls_test_ssl_exchange_data(
+                        &(client.ssl), options.cli_msg_len,
+                        options.expected_cli_fragments,
+                        &(server.ssl), options.srv_msg_len,
+                        options.expected_srv_fragments)
                     == 0);
     }